The invention relates to a torque wrench for tightening and braking-out threaded joints between drill pipe and drill collar sections forming parts of a drill string.
The background of the present invention includes the problems and the amount of work needed related to inserting and unscrewing drill pipes on the drill floor during drilling operations, particularly with regard to inserting and removing a drill string into/from a drilling well in a tripping operation.
During the last 10 to 20 years, hydraulic/mechanical equipment was available to facilitate such operations. Equipment of this kind is called a roughneck, and one concept is shown in U.S. Pat. No. 4,348,920. In short, such a roughneck comprises a two-piece lower unit the lowermost member of which forms back-up wrenches, whereas the upper member acts as a torque tong or wrench. Such a wrench encircling grips a drill pipe joint, and, in a conventional drilling operation, the back-up wrenches will clasp the sleeve portion of the joint, and the torque wrench will clasp the tap portion of the joint. The wrench causes the final torque make-up, or breaking-out, respectively, between pipe sections, whereas the upper spinning means causes the pipe sections to be screwed in, or unscrewed, respectively. A similar concept is shown in U.S. Pat. No. 4,603,464.
Existing equipment is, obviously, limited as regards flexibility in case of changed diameters or dimensions. A drill string may comprise drill pipes having a diameter of 3,5" with a joint diameter of 4.5", and drill collars with diameters up to 9.5". With existing equipment, it is common practice to replace jaws in the gripping jaws of tongs at least once, perhaps twice, to accomodate diameter variations. Also, many tools lack capacity for the largest diameters.